In many different technical fields there is a need to arrange thin layers of a conducting material on a non conducting substrate. In the manufacturing of electronic components this need is evident. Circuit boards are an example of products, where materials with different conducting properties are required to be combined with a large precision and a high resolution. Nowadays ever increasing demands are put on both the production processes and the products. The methods mainly used nowadays to produce circuit boards are subtractive. This implies that one starts from a substrate provided with a conductor, from which substrate the conducting material is removed in several successive steps from the surfaces where an electric conducting capacity is not desirable.
In traditional manufacturing of circuit boards one starts from a substrate or a basic laminate, in which a hole picture is drilled to allow the application components and/or connection of conducting layers on opposite sides of the substrate. On the substrate is thereafter deposited a conducting material in the holes, usually copper. Then, a thin light sensitive film is applied over the substrate, often under high pressure and high temperature. On this film a photographing tool is placed in form of a negative picture of the desired circuit pattern, the photographing tool then being exposed to UV-light, the film thereby polymerizing in the exposed areas. The exposed, light sensitive film is developed and the non polymerized areas are washed off by means of a suitable base. The desired circuit pattern is thus enclosed by the remaining film. Then, a metal e.g. copper is electrolytically plated, according to this pattern. Over this pattern tin or lead is plated, whereafter the film is removed in a bath, e.g. by means of a strong base. Thereafter, the layer of tin or lead is etched off, whereafter a liquid soldering masque is applied, e.g. in form of an epoxy color with two components. The soldering masque is exposed and developed and finally a protective layer in nickel or gold is applied to prevent any oxidation.
This method involves several drawbacks. Firstly the production process is very labor intensive leading to that the production of circuit boards is to a large extent being transferred to countries with low labor costs. Secondly large quantities of residues harmful to the environment are formed, mainly in the form of etching fluids with high metal contents, e.g. copper, lead, tin, etc. Thirdly the existing production methods do not comply with the increasing technical demands. The conventional methods are approaching their inherent limits, especially regarding the line width.
Thus, there is an apparent demand to simplify the production processes, to increase the automatisation level and to simultaneously remove the environmental problems connected with the present use of reactive chemicals and metals in solution. Simultaneously a lot of research and development efforts are aiming at making both electronic components and circuit boards less material and space consuming. The production of circuit boards is here below presented as an example for one of the many applications, for which the present invention is applicable.